There has been suggested a rocker arm 95 that is rockably supported by a rocker shaft 99 and that is assembled such that a lash adjuster 90 that adjusts a valve clearance is fitted in a fitting hole 96 provided in a closed-end hole shape as shown in FIG. 8 (Patent Literature 1).
The lash adjuster 90 is prevented from slipping off from the fitting hole 96 by bringing the distal end of a plunger 91 into contact with an inner bottom face 97 of the fitting hole 96 and increasing the diameter of a snap ring 94 inside a large-diameter portion 98. The snap ring 94 is fitted in a snap ring groove 93 provided in the outer circumferential surface of a body 92. The large-diameter portion 98 is formed at the bottom side of the fitting hole 96.